This application claims the benefit of Korean Patent Application No. P2002-11193 filed on Mar. 02, 2002, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
The present invention relates to a sputtering apparatus, and more particularly, to a sputtering target assembly and a sputtering apparatus using the same. The present invention is especially applicable in enhancing target utilization in a magnetron sputtering apparatus.
2. Description of the Related Art
Recently, image display units have changed from a cathode ray tube (CRT) display to a flat panel display such as liquid crystal display devices and plasma display panels. When compared to a cathode ray tube, a liquid crystal display device has lower power consumption, can be manufactured to be lighter and thinner, and does not radiate any harmful electromagnetic waves. Thus, the liquid crystal display device is well suited for the next-generation high-technology image display apparatus.
FIG. 1 is a schematic view showing a structure of a typical liquid crystal display device. Referring to FIG. 1, a typical liquid crystal display device includes a thin film transistor (hereinafter referred to as TFT) substrate, a color filter substrate, a liquid crystal layer, and a backlight unit. A TFT array is formed on the TFT substrate, and color filters are formed on the color filter substrate. The liquid crystal layer is formed between the TFT substrate and the color filter substrate. The backlight unit provides light to display an image.
Here, the TFT array formed on the TFT substrate transmits and controls an electrical signal, and the liquid crystal layer controls the degree or amount of transmittance according to an applied voltage. The light controlled through these procedures passes through the color filter substrate so that desired colors and images are displayed.
When a black matrix layer is formed on the color filter substrate or an electrode is formed on the TFT substrate, a metal such as chrome (Cr) is deposited using a sputtering apparatus. Here, in a thin film forming method using a sputtering process, a target formed of a desired thin film material is disposed within a vacuum chamber, and a substrate is disposed at a position corresponding to the target. Then, argon (Ar) ions are injected. Collision particles, such as argon (Ar) particles, ionized due to plasma formed within the vacuum chamber collide with a surface of a negatively charged target. Particles come off of the target or are sputtered due to the collision energy and are deposited on the substrate.
The thin film forming method using the sputtering process includes, for example, a diode sputtering method, a bias sputtering method, a high frequency sputtering method, a triode sputtering method and a magnetron sputtering method. In case of the widely used magnetron sputtering method, a magnet is mounted on the back surface of the target. Therefore, in the sputtering process, since a higher density of plasma is formed at a target region where the magnet exists than other regions, more target atoms are emitted, thereby enhancing the deposition rate of the thin film.
However, unlike these advantages, as the sputtering process is performed, a target erosion rate is high for a specific portion, which degrades the whole utilization of the target.
Presently, it is possible to implement various magnetron sputtering apparatuses. FIG. 2 is a conceptional view showing an erosion state of the target according to the location of the magnet in a typical magnetron sputtering apparatus. As shown in FIG. 2, an erosion topology of the target 21 is different according to a location of the magnet 23.
Referring to FIG. 2, when the sputtering process is performed using the magnet in the typical magnetron sputtering apparatus, a partial erosion of the target 21 occurs due to a uniform division of a magnetic field. Thus, the sputtering deposition is performed using only a portion of the target 21, resulting in an ineffective utilization of the target.
To improve these disadvantages, a magnetron sputtering apparatus has been provided using a moving magnet, in which the fixed magnet 23 becomes a moving magnet. In such magnetron sputtering apparatus using a moving magnet, however, the target 21 still does not erode uniformly in all the regions. Moreover, the erosion occurs partially in a non-uniform manner.
Thus, to effectively use the target, the target is divided and is formed with different thicknesses according to the location of the target, taking into account the non-uniform erosion tendency of the target.
FIG. 3 is a schematic view showing a topology of a conventional sputtering target assembly employed in the typical magnetron sputtering apparatus. As shown in FIG. 3, targets 35 and 37 of a sputtering assembly 30 are divided with different thickness according to the location thereof. The targets 35, which are formed to be relatively thick, are in regions where over-erosion occurs, and the target 37, which is formed to be relatively thin, is in a region where less erosion occurs. Thus, a step topology is formed. By leveling the surfaces of the targets 35 and 37 and applying the step topology to an appropriate region of the backing plates 31 and 33, a region of the backing plate 31 (in which only the back plate 31 is formed) corresponding to the over-erosion region 35 of the targets is protected and the utilization of the targets 35 and 37 can be enhanced and maximized.
Here, the erosion topology of the targets 35 and 37 is theoretically calculated for the magnetron sputtering apparatus and its operating condition. The degree of step of the backing plates 31 and 33 is determined according to the thickness of each location of the calculated targets 35 and 37.
During the sputtering process in actual production using the magnetron sputtering apparatus employing the backing plates 31 and 33 (which are designed with the step thereon) an operating condition may be changed according to different production models. Such change in the operating condition also changes the theoretically calculated erosion topology of the targets. Here, a problem occurs in that the backing plates 31 and 33 should also be modified/redesigned so as to correspond to the newly changed operating condition.
Since the backing plates 31 and 33 are modified/redesigned according to the changed operating condition, the backing plates 31 and 33 tend to be articles of consumption in the production, which increases cost.
Accordingly, the present invention is directed to sputtering target assembly and sputtering apparatus that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Accordingly, an advantage of the present invention is to enhance the utilization of the sputtering targets.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a sputtering target assembly is provided including a backing plate having two evenly formed surfaces and a target having one portion evenly formed and on one surface of the backing plate and another portion having a different thickness from the one portion. The target can be made having a divided structure according to its thickness. Thus, different sections or portions of the target have different thicknesses. The target also has a region where there is a tendency for over-erosion, thus being formed relatively thicker.
According to another aspect of the present invention, a sputtering apparatus is provided including a sputtering target assembly having a backing plate having two evenly formed surfaces and a target having one evenly formed surface and on one surface of the backing plate and another surface having a different thickness at a different location, and a magnet below a bottom surface of the backing plate, the magnet generating a magnetic field at the targets. The magnet can be a moving magnet that moves below the bottom surface of the backing plate. The target can be made having a divided structure according to its thickness. Thus, different sections or portions of the target have different thickness. The target also has a region where there is a tendency for over-erosion, thus being formed relatively thicker.
Thus, when an erosion topology of the targets is changed due to a change in the sputtering apparatus or operating condition, target utilization can be enhanced by changing only the topology of the targets without modifying/redesigning the backing plate.
In another aspect of the present invention, a sputtering target assembly comprises a backing plate having first, second and third regions; a first target corresponding to the first region of the backing plate; a second target corresponding to the second region of the backing plate; and a third target corresponding to the third region of the backing plate,
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.